Clean tech companies have traded flat on aggregate this year versus the S&P 500’s 2-percent gain, a sharp contrast from when it was the best-performing energy subsector.

Yet clean tech "remains a stock picker’s market,” Raymond James analyst Pavel Molchanov said in a Thursday note. First Solar, Inc. (NASDAQ: FSLR) stock is down 22.6 percent in the first half of 2018, while Enphase Energy Inc (NASDAQ: ENPH) is up 197 percent.

The Ratings

Advanced Energy Industries was upgraded from Market Perform to Outperform with a $72 price target.

Clean Energy Fuels was downgraded from Market Perform to Underperform.

NextEra Energy Partners was downgraded from Outperform to Market Perform.

The Thesis

Shares of Clean Energy Fuels closed Tuesday at $3.71, up 82.8 percent for the year. What is striking about the stock’s rally is that it occurred almost entirely after the company announced a partnership with Total SA (NYSE: TOT) on May 10.

Investors looking to support their bull case should watch for any news out of Congress on the Alternative Fuels Tax Credit, which was retroactively reinstated in February to cover 2017 — although it seems unlikely Congress will move to revive the credit before the midterm elections, if at all, Molchanov said.

The company saw revenue grow 39 percent in 2017, but Molchanov projects that rate will halve in 2018 and further slow to 4 percent in 2019. He attributes this to improvement in the industrials segment being counterbalanced by the maturing of the 3-D NAND upcycle.

Advanced Energy Industrials is a “blend of multiple cyclical businesses, whose cycles may or may not cancel each other out at any given time,” the analyst said.